A process for the manufacture of 7-(imidazol-2-yl)amino-3-(1H-1,2,3-triazol-4-yl)thiomethylceph-3-em-4-carboxylic acid, and the acid- and base-addition salts thereof, characterised by reaction of a compound of the formula 1: in which R¹ is a displaceable radical with 4-mercapto-1H-1,2,3-triazole or a base-additional salt thereof in a diluent or solvent consisting of trifluoroacetic acid, trichloroacetic acid, acetonitrile or sulpholane, or a mixture of any two or three of these, in the presence of boron trifluoride or a complex thereof;

whereafter when the product is obtained as the free base or the salt, and the salt or free base respectively is required, the interconversion between salt and free base is carried out by conventional means.